Modern electrophotographic ("EP") printers use some sort of processor to interpret a program representing the image to be printed. The program is written in some sort of graphical description language, and the interpretation involves conversion of the program into an intermediate format, such as a display list. This display list is subsequently used to create a bitmap, which determines a pattern of light. In a typical EP printer, this pattern of light exposes a photosensitive drum. The exposure results in a charge pattern on the drum. The drum rotates past a toner dispenser and attracts toner particles to the drum's surface corresponding to the charge pattern. The drum transfers the toner to a print medium such as a piece of paper. The toner is fused to the paper, and the paper exits the printer.
The exposure unit that provides the pattern of light for exposing the drum can be comprised of a laser-scanning device or a spatial light modulator. Spatial light modulators are becoming the technology of choice for full-color, high-resolution printing at increasingly faster speeds. As printer hardware improves, methods are needed for providing faster processing, i.e., the interpretation of graphical description programming to bitmap data.
Some recently developed printers use "multiprocessors", which use a master processor and at least one subprocessor. Typically, a number of subprocessors operate in parallel. Multiprocessors often have a limited instruction cache size and the cost of instruction cache misses is high.